Those options - Rally Stripes & Hurst Shifter - can be included tomorrow or added anytime before the order is pulled for production, probably months down the road. The Performance exhaust must be ordered separately, and you cannot do that yet. I'm no authority, but I would bet big $ he's wrong about adding GMPP parts later decreasing your warranty. Sounds like a dumb salesman feeding you
Get a printout of the "Order Workbench" which will show what you're buying - trim line, colors, options - and, most importantly, your alphanumeric order number - top left.
Enjoy!